Engineers are overcoming challenges to maximize the number of satellites launching on a single rocket
As of November, 564 nanosatellites have been launched into space. In January, the Indian Space Research Organisation aims to launch a combination of 83 satellites on a single rocket—reportedly a world record. Then in February, U.S. startup Spaceflight Industries plans to piggyback its launch of a module that can support up to 87 satellites onto another space rocket.
Neither the Indian Space Research Organisation (ISRO) or its commercial arm, Antrix Corporation, responded to requests for comment. But Spaceflight Industries senior mission manager Adam Hadaller described putting together launch missions for small satellites as “herding cats… It’s very hard.”
Once you get them in space, nano, cube, and other small-scale satellites have several applications—from monitoring weather to helping farmers decide where to water or fertilize crops—all at a significantly lower price than traditional-scale satellites. Several startups and space agencies, such as ISRO and Spaceflight Industries, are working to launch more and more of them at the same time, further reducing costs.
The first challenge begins before launch, Hadaller says. Satellites can come from different countries and it’s necessary to check all the various safety regulations, communication licenses, and technical requirements. The different separation systems, for example, need compatible adapters.
Then, there is a choice to make: Piggyback the satellites as secondary payload on a rocket that’s already heading to space, or have a dedicated mission?
In February, a SpaceX Falcon 9 rocket could launch with the Spaceflight Industries module called SHERPA—containing small satellites—as secondary payload. In the mission, Falcon 9 will launch its primary payload and then deploy SHERPA after an orbital maneuver. Half an hour later, SHERPA will release its satellites.
Hadaller says that in the case of the SHERPA mission, the main limitation of the module itself is interest: As of 12 December only 33 satellites were on the passenger manifest.
However, when piggybacking, satellites don’t have much choice for their orbits, which limits the variety of possible scientific experiments. Some companies, such as Orbital ATK, are trying to get around this by launching single-purpose rockets that can launch satellites to targeted orbits.
For example, on 12 December, Orbital ATK launched a Pegasus rocket containing eight CubeSats designed to monitor hurricane development in the tropics. The satellites deployed at a 510-km altitude at an inclination of 35 degrees—over time they spread out over the entire orbit. As they continue orbiting, their inclination moves them no more than 35 degrees above or below the equator, giving full coverage of the tropics, as desired.
But whether it be from ridesharing or targeted-purpose rocket launches, after deployment, satellites still need to communicate with the ground. Launching so many small satellites at the same time creates new difficulties.
Usually, satellite owners communicate with their satellites over radio by pointing antennas on the ground at satellite locations. The better the aim, the stronger the signal, so satellite operators can find their satellite’s location by using some combination of onboard GPS, trajectory estimation data, large telescope arrays, the JSpOC satellite tracker, or radio ranging—sending a radio query into space and finding their positions by considering the timings and Doppler shifts of hit objects.
Bruce Yost directs a NASA institute for small satellite outreach called the NASA Small Spacecraft Systems Virtual Institute. He says one problem with radio is too may things trying to talk in the same space, so to speak. If the small satellites can be identified, then the frequencies they often use to communicate can be crowded with ground-based radios, cell phones, and other satellites.
One solution is to communicate at higher frequencies, but this requires extra power. Another, less power-hungry solution researchers are considering would be transmitting data from space to ground with lasers—the drawback being that the optical link would need “even more accurate pointing” than radio communications.
There’s also a risk of all these new satellites just existing. Some have raised concerns that they could pose a risk of becoming debris.
Spaceflight Industries says the team has not run an updated analysis of the exact probability of its satellites colliding with each other or another object in space, but Hadaller says it is “extremely low.” Also, all the tech meets international space community requirements of not staying in low Earth orbit for more than 25 years. SHERPA will stay in orbit for 10 to 18 years and the satellites between three and 10 years, before they re-enter Earth’s atmosphere and burn up.
Mike Safyan, Director of Launch and Regulatory Affairs at Planet Labs, an Earth imaging company that makes small satellites, believes that the demand for launching large numbers of rockets is low for now, but “if the companies are successful, then we’ll see more of these kind of large cluster launches.”
Yost says that there will be at least five NASA-sponsored, small, cube-shaped satellites called CubeSats on the upcoming Spaceflight Industries launch, which has been delayed from late 2016 to 2017.
“The capability of these CubeSats is really, really advancing quickly,” he says. Advancements in computer processors have made it possible to do “extensive” data processing and analysis directly onboard a small satellite. Advancements in design and fabrication are also making them more robust to the harsh environment of space.
Jordi Puig-Suari, an aerospace engineer at California Polytechnic State University in San Luis Obispo, helped design the original concept for CubeSats. He says “the timeline is one thing that we have to work on.” He says “the satellites can be developed very quickly,” but getting them into space might not happen at the same speed.
Of course, the benefits are clear. “Having a larger number of lower-cost missions will allow us to go to a lot more places,” Puig-Suari says.